Two-stage trigger mechanism for firearms

ABSTRACT

A multi-stage trigger mechanism for a firearm having a trigger body that is pivotally mounted to the receiver of a firearm having a pivotally moveable spring-urged hammer having a trigger hook and a hammer hook. A disconnector is pivotally mounted to the trigger body and has a spring retainer securing a disconnector spring to the disconnector. The disconnector has a hook member defining a timing surface that serves to delay hammer reset and provides enhanced trigger hook engagement to prevent doubling during firing activity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to firearms, particularlyfirearms having trigger assemblies that are cocked or made ready forfiring by rearward movement of a bolt or bolt carrier within a receivermechanism of a firearm. More particularly, the present inventionconcerns a two-stage trigger mechanism having a first stage that isactivated by movement of a trigger member by application of a desiredfirst stage manual trigger force and a second stage that is activated byfurther movement of the trigger member by application of a desiredsecond stage manual force. This invention also concerns the provision ofangulated surfaces on the disconnector of the trigger mechanism toprovide for dual stage operation and to minimize any potential for firedround doubling.

2. Description of the Prior Art

Every firearm has historically been provided with a trigger mechanism toprovide the user with the capability for simple and efficient control offirearm discharge. Multi-stage trigger mechanisms are well known in theart, as exemplified by U.S. Pat. No. 7,600,338 of Geissele. This patentdiscloses a two stage trigger mechanism that is designed particularlyfor M16 or AR15 type semi-automatic rifles which are widely utilized bythe United States Military and by the public. Some commerciallyavailable multi-stage trigger mechanisms are adjustable, such a taughtby U.S. Pat. Nos. 6,131,324 of Jewell, 5,501,134 and 5,881,485 ofMilazzo. Some adjustable multi-stage trigger mechanisms suffer from theuncertainty of adjustment screws or set screws which can become loose ormove during firing activity, thereby changing the operational characterof the trigger mechanisms. U.S. Pat. No. 8,074,393 of Geissele alsoevidences a multi-stage trigger mechanism having a sear face that can beadjusted and having a disconnector spring that can also be adjusted bymeans of a spring force adjustment screw.

SUMMARY OF THE INVENTION

It is a principal feature of the present invention to provide a novelmulti-stage trigger mechanism for rifles such as M16 or AR15 typesemi-automatic rifles as well as a wide variety of other rifles andfirearms which are provided with a coil type disconnector spring havingan end portion that is interposed between the disconnector and triggerbody and is secured to the disconnector so as to be moveable with thedisconnector during operation of a trigger mechanism.

It is another feature of the present invention to provide a novelmulti-stage trigger mechanism having a trigger body to which ispivotally mounted an elongate spring urged disconnector and having adisconnector stop member projecting from the trigger body and serving toensure against pivotal over-travel of the disconnector as cycling of thetrigger mechanism occurs.

It is also a feature of the present invention to provide a disconnectorgeometry that ensures holding the hammer down longer during reset,thereby creating significantly more engagement between the hammer hookand the trigger hook.

Briefly, the various objects and features of the present invention arerealized through the provision of a multi-stage trigger mechanism thatis designed particularly for tactical firearms, such as the M-16military version and the AR-15 civilian version and is well adapted forfiring control of many other types of firearms. The invention isdiscussed herein particularly as it relates to M-16 and AR-15 tacticalrifles. This type of firearm incorporates a lower receiver which ispivotally mounted to an upper receiver, as is well known. The lowerreceiver defines an internal compartment within which a triggermechanism is mounted for firing control of a torsion spring urged hammerthat is pivotally mounted within the lower receiver compartment.

The trigger mechanism of the present invention incorporates a triggerbody member which is pivotally mounted to the receiver of the firearmand is urged toward its safe position by means of a torsion springhaving a pair of torsion loops that are located about pivot bearings ofthe trigger body. The trigger body defines a trigger sear hook that isengaged by a sear hook of a spring urged hammer that is also pivotallymounted to the receiver of the firearm.

A disconnector member is pivotally mounted to the trigger body and isurged by a disconnector spring to a position for engagement of thehammer engaging cam surface geometry thereof with an angulated camsurface of the trigger member. The cam surface of the disconnector has asubstantially straight surface portion that is engaged by the searprojection of the hammer member. The disconnector geometry also includesan angulated surface portion that establishes a hammer timing surface ofgreater length than is conventional, which holds the hammer down longerduring reset. This feature creates more engagement between the hammerhook and the trigger hook and has the effect to preventing the triggermechanism from inadvertently permitting doubling when the trigger isoperated during firing activity.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages andobjects of the present invention are attained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to the preferred embodimentthereof which is illustrated in the appended drawings, which drawingsare incorporated as a part hereof.

It is to be noted however, that the appended drawings illustrate only atypical embodiment of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

In the Drawings:

FIG. 1 is an isometric illustration showing the lower receiver of anM-16 or AT-15 tactical rifle in broken line and showing a trigger andhammer mechanism embodying the principles of the present inventionmounted within the lower receiver;

FIG. 2 is a side elevation view showing the trigger and hammer mechanismof FIG. 1 in greater detail;

FIG. 3 is an isometric illustration showing the multi-stage trigger andhammer mechanism of FIG. 2 and showing the side and top portionsthereof;

FIG. 4 is an enlarged section view showing the relationship of thehammer hook the trigger hook and the disconnector mechanism of thisinvention;

FIG. 5 is a side elevation view of the disconnector of FIG. 4 showingthe angulated disconnector surfaces for control of hammer and triggerreset; and

FIG. 6 is a fragmentary elevation view showing a portion of thedisconnector structure of FIG. 5 and emphasizing disconnector surfacearea enhancement for timing of hammer movement.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the drawings and first to FIG. 1, a lower receiver ofan M-16 or AR-15 tactical rifle is shown generally at R and defines aninternal compartment C within which a multi-stage trigger mechanismembodying the principles of the present invention is shown generally at10. The multi-stage trigger mechanism incorporates a trigger body 12having a trigger projection 14 defining a curved trigger engagementsurface 16 to which is applied manual force of the user's finger todischarge the firearm. The trigger body defines a pivot aperture 18which extends through bearing or bushing projections 20 and 22 thatproject from opposite sides of the trigger body. A pivot pin 24, alsoreferred to as a trigger pin, is positioned within the pivot aperture 18and serves to establish pivotal mounting of the trigger body 12 to thereceiver of a firearm.

Opposite end portions of the trigger pin 24 project axially beyond theaxial end portions of the bearing members 20 and 22 and are engagedwithin pivot pin receptacles of a firearm receiver 23, thus pivotallymounting the trigger body to the firearm receiver. A rear end portion ofthe trigger body 12 defines a trigger rotation limit projection 26having a downwardly facing curved surface 28 that establishesessentially line contact with a trigger stop surface 30 of the firearmreceiver 23, preventing further clockwise pivotal rotation of thetrigger body as shown in FIG. 2.

The bearing or bushing projections 20 and 22 are of generallycylindrical configuration and also serve as trigger spring mountprojections that encircle and provide support for circular loop portionsof a torsion type trigger spring 32. A U-shaped portion 34 of thetrigger spring 32 extends about a forward end portion of the triggerbody, forwardly of the trigger projection 14, and continuously appliesrotational spring force to the trigger body 12. The trigger spring has apair of reaction projections 36 and 38 that contact portions of thefirearm receiver and serve to apply a torsion spring load to the triggerspring. The reaction projections are placed under load during triggerassembly so that the torsion spring loops apply clockwise rotationalforce to the trigger body as shown in FIG. 2 to maintain the triggerrotation limit projection 26 in contact with the trigger stop surface30.

A hook-like trigger sear 40 projects upwardly from the trigger body 12and defines a downwardly facing trigger sear surface 42 that is engagedby a hammer sear hook 44 of a hammer member 46. The hammer member 46defines an upwardly facing hammer sear surface 45 that is disposed forengagement with the trigger sear surface 42 to secure the hammer againstpivotal firing pin striking movement. The hammer member 46 is pivotallymounted to the firearm receiver by a hammer pin 48 that extendscrosswise through a pivot aperture 50 of the hammer. The hammer memberdefines a safety sear notch 37 that is disposed for engagement by anabrupt end corner 39 of the trigger body member 12 to provide a safetysear for preventing the trigger from inadvertent resetting rotationbefore the hammer is reset by its torsion springs.

Bearing or bushing members 52 and 54 of the hammer member 46 areencircled by loops 56 of a torsion type hammer spring 58. The hammerspring 58 defines a U-shaped portion 60 having spring arms 59 thatextend from each of the spring loops 56. The hammer spring 58 also has apair of spring arms that engage end portions of the hammer pin or engagethe outer cylindrical surfaces of the oppositely projecting bearing orbushing members 52 and 54. These spring arms are yielded during assemblyto provide a continuous rotational force on the trigger member. As thehammer member is pivotally moved to its set or cocked position byrearward movement of the bolt carrier or bolt of the firearm the torsionforce of the trigger spring is increased substantially, so that releaseof the hammer by trigger actuation will permit the trigger spring todrive the hammer member pivotally forward. The hammer strikes the firingpin of the firearm with sufficient force to deform the metal of theprimer of a cartridge within the cartridge chamber of the firearmbarrel, igniting the primer and causing the powder of the cartridge tobecome ignited and generate cartridge gas pressure that propels a bulletfrom the cartridge through the rifled bore of a barrel.

A disconnector member 62 is pivotally mounted to the trigger body 12 bya pivot pin member 64 and has its pivotal movement limited by thedownwardly facing stop surface 65 of a disconnector stop member 66 thatprojects upwardly from the trigger body 12. The trigger body defines adisconnector recess 63 that is formed in part by spaced pivot supportflanges 67 which have pivot openings receiving the pivot pin 64. Thedisconnector also defines a transverse pivot opening or bore throughwhich the pivot pin 64 extends. To ensure an interference fit of thepivot pin 64 within the disconnector, a transverse slit 69 is formed inthe disconnector and intersects the transverse pivot bore 71 withinwhich the pivot pin 64 is received. This feature permits the pivot pinto be press-fitted within the transverse pivot bore 71, yielding themetal structure at each side of the slit 69, thereby establishing a firmnon-rotatable relation of the pivot pin with the disconnector structure.If desired, a roll pin defining a lateral slit may also achieve animmoveable interference fit with the transverse passage or bore 71 ofthe disconnector.

A portion of the disconnector is received between the spaced supportflanges of the trigger body 12 to provide for stability of hammermovement during firing and return rotation. The disconnector defines adisconnector hook 68 having a hammer engagement surface cam surface 84that is engaged by first and second stage trigger activity. An angulatedsurface 70 of the disconnector that is disposed for engagement with anangulated surface 72 of a disconnector projection 73 of the hammermember 46. The rounded nose 67 of the disconnector projection 73 hascontact with the surface 84 of the disconnector hook 68 as discussed indetail in connection with FIG. 5. Engagement of the surface 70 of thedisconnector member and the surface 72 of the hammer establishes thefirst stage of trigger movement during which the hammer is out ofengagement with the disconnector member and is then engaged and retainedby the downwardly facing hammer sear surface 42 of the hook-like triggersear 40 of the trigger body member during pivotal return of the hammerafter firing activity has taken place.

The disconnector also defines an end surface 88 that extends from thesurface 84 and is oriented in angular relation with the surface 84. Thepurpose of the angulated end surface 88 is to provide the angulatedsurface 70 of the disconnector with maximum length so that it serves asa timing surface to cause return delay of the hammer sufficiently tominimize the potential for inadvertent doubling or automatic fire of thefirearm.

The trigger body 12 defines a disconnector spring pocket 74 within whichthe lower end portion of a disconnector spring 76 is received. Thedisconnector spring 76 is preferably a coil type compression spring;however it may conveniently take the form of a leaf spring, wave spring,or any other suitable type of spring that tends to rotate thedisconnector in the counter-clockwise direction as shown in FIG. 2. Thelower portion of the disconnector defines an undercut spring retainermember 78 that defines a spring receptacle 80 within which the uppercoil portion of the disconnector spring is mounted to the disconnector.The upper portion of the spring 76 may be essentially threaded into anupper spring receptacle 77, shown in broken line in FIG. 4 to permitadjustment of the spring force acting on the disconnector member. Thus,the disconnector spring is mounted to and travels with the disconnectorand can be adjustable to increase or decrease its spring force.

The undercut spring retainer member 78 maintains the upper coil of thedisconnector spring centered within the spring receptacle and thusensures that the disconnector spring cannot become inadvertentlymisaligned. Thus, the force of the disconnector relative to the hammersurface 72 is efficiently maintained so that the trigger pull forces ateach of the operational stages of the trigger mechanism always have thesame feel to the user of the firearm.

lever 82 is aligned with a safe marking on the lower receiver. To permitfiring activity the safety lever 82 is rotated, typically about 45°counter-clockwise, to a “semi” marking on the receiver. This rotationmoves the safety surface of the shaft 80 to a position that is clear ofthe trigger body and permits sufficient pivotal movement of the triggerbody for firing when the user of the firearm applies manual force to thesurface 16 of the trigger 14.

With reference to FIG. 5, the hook portion 68 of the disconnector member62 defines a relatively long second stage hammer engaging cam surface 84having substantially straight sections 86 and 88 that have angularintersection at 90. This feature causes the hammer engagement surface 70of the disconnector to have a greater length than usual, this greaterlength being established by the disconnector surface increment 92 thatis identified in broken line. This feature establishes greater or longerduration surface engagement between the hammer hook and trigger hook,thus causing the hammer to be held down longer during reset, as comparedwith conventional trigger mechanisms with straight hammer engaging hooksurfaces. The second stage of trigger operation occurs when the camsurface 84-86 of the disconnector hook comes into contact with thehammer projection 73. This hammer delay is characterized as a timingsequence during hammer return which establishes greater surface tosurface engagement of sear surfaces 42 and 45 of the trigger and hammersears and prevents inadvertent doubling or automatic fire. The triggermechanism will release the hammer for spring urged rotation andcartridge firing before the angulated disconnector surface 88 is reachedby hammer movement along the cam surface 84 of the disconnector hook 68.Thus, the angulated surface 88 is not intended to be contacted by thehammer projection 73 and is provided for the primary purpose of ensuringthe maximum length of the disconnector hook cam surface 70 to providefor hammer delay during reset.

Operation

The two-stage firing mechanism of the present invention will begin itscycle of operation with the trigger mechanism being in the conditionshown in FIG. 3, with the hammer sear surface 45 of the hammer 46 beingin surface to surface engagement with the trigger sear surface 42 of theof the trigger sear member 40. At this stage of trigger operation thehammer engaging surface 84 disconnector hook 68 will be clear of thedisconnector engaging projection 73 of hammer member 46. The rearportion of the disconnector member 62 will be in engagement with thedownwardly facing stop surface 65 of the disconnector stop member 66 andcan only be moved pivotally downward against the bias of thedisconnector spring 76 about the pivot pin 64.

The user of the firearm will then apply manual finger force on thecurved surface 16 of the trigger, this force being in the range of abouttwo pounds to overcome the bias of the torsion springs 32 and causingrotation of the trigger body 12 about the pivot pin 24 and also causingrotation of the disconnector member 62 about the trigger pivot pin 24and causing the hammer engaging surface 84 of the disconnector hook 68to come into contact with the disconnector engaging projection 73 of thehammer 46. At this point in the firing process the sear surfaces 42 and45 will have sufficient surface to surface engagement that the firearmremains safe will not accidentally discharge. When this contact is made,the resistance of the disconnector caused by the disconnector springwill add to the force or pull that is experienced by the firearm user,indicating that the first stage of trigger operation has been completedand that a greater finger force must be applied, i.e., the second stage,in order to achieve hammer release for striking the firing pin andfiring a round. This additional finger force is typically in the rangeof about an two pounds, but can be more or less according to the designof the trigger mechanism.

When second stage resistance is encountered, the additional force willovercome the resistance of the disconnector spring 76, causing thedisconnector to move about its pivot 64 and allowing further surface tosurface movement of the sear surfaces 42 and 45 to occur. Only minutemovement of these sear surfaces is necessary to achieve trigger breakand release the hammer for its spring urged pivotal movement to strikethe firing pin of the firearm. The second stage trigger activity willoccur while the sear projection 73 is in contact with the cam surface 84of the disconnector and before the sear projection reaches the angulatedor offset surface portion 88 of the disconnector hook 68.

As mentioned above particularly in connection with FIGS. 4 and 6, thedisconnector hook 68 has an angular surface 88 having the purpose ofproviding the angulated surface 70 with sufficient length to be engagedby the surface 72 of the hammer 46 during hammer return after firingactivity and to establish sufficient hammer reset delay to provide muchmore sear surface engagement of the sear surfaces 42 and 45 preventingthe occurrence of doubling or automatic firing activity. After theforegoing trigger and hammer activity has occurred, the triggermechanism will have been reset for another semi-automatic firingsequence.

In view of the foregoing it is evident that the present invention is onewell adapted to attain all of the objects and features hereinabove setforth, together with other objects and features which are inherent inthe apparatus disclosed herein.

As will be readily apparent to those skilled in the art, the presentinvention may easily be produced in other specific forms withoutdeparting from its spirit or essential characteristics. The presentembodiment is, therefore, to be considered as merely illustrative andnot restrictive, the scope of the invention being indicated by theclaims rather than the foregoing description, and all changes which comewithin the meaning and range of equivalence of the claims are thereforeintended to be embraced therein.

I claim:
 1. A multi-stage trigger mechanism for a firearm, comprising: atrigger body having a mounting pin mounting said trigger body to thereceiver of a firearm having a pivotally moveable spring-urged hammerhaving a trigger hook and a hammer hook, said trigger body defining aspring receptacle; a disconnector being pivotally mounted to saidtrigger body and defining a spring retainer structure; and adisconnector spring having a first portion thereof mounted to saidspring retainer structure and having a second portion thereof disposedwithin said spring receptacle, said disconnector spring being moveablewith said disconnector and applying spring force to said disconnectorand said trigger body.
 2. The multi-stage trigger mechanism of claim 1,comprising: said disconnector spring being a coil type compressionspring having generally circular first and second ends; said springretainer being a spring retainer projection having an undercut portiondefining a spring opening and retaining said first end of said coil typecompression spring.
 3. The multi-stage trigger mechanism of claim 1,comprising: a disconnector stop member being defined by said triggerbody and having a stop surface limiting spring urged pivotal movement ofsaid disconnector relative to said trigger body.
 4. The multi-stagetrigger mechanism of claim 1, comprising: a trigger rotation limitprojection being defined by said trigger body and being disposed forcontact with a firearm receiver and preventing over-rotation of saidtrigger body.
 5. The multi-stage trigger mechanism of claim 1,comprising: a hammer engaging cam surface being defined by saiddisconnector; and a disconnector sear being defined by said disconnectorand having a hammer engagement cam surface and a disconnector searprojection establishing a hammer return cam surface of sufficient lengthto hold said hammer down sufficiently to prevent following, a portion ofsaid hammer engagement cam surface being a second stage cam surface. 6.The multi-stage trigger mechanism of claim 5, comprising: said hammerengaging cam surface being of substantially planar configuration; andsaid disconnector sear projection establishing a surface disposed inangular relation with said hammer engaging cam surface.
 7. Themulti-stage trigger mechanism of claim 1, comprising: a pair of spaceddisconnector mount flanges being defined by said trigger body and havingapertures formed therein; and a pivot pin extending through saidapertures of said spaced disconnector mount flanges and through saiddisconnector member and mounting said disconnector for pivotal movementabout said pivot pin.
 8. The multi-stage trigger mechanism of claim 5,comprising: said disconnector having a hammer contact surface and atiming surface having intersection with said first surface and beingdisposed in angular relation with said hammer contact surface, saidangular timing surface causing said hammer contact surface of saiddisconnector to be of sufficient length to hold said hammer down duringreturn for a sufficient period of time to prevent doubling during firingactivity.
 9. A multi-stage trigger mechanism for a firearm, comprising:a trigger body having a mounting pin mounting said trigger body to thereceiver of a firearm having a pivotally moveable spring-urged hammerhaving a trigger hook and a hammer hook and defining a hammer searsurface and defining a disconnector engaging projection; a disconnectorbeing pivotally mounted to said trigger body and having a disconnectorhook defining a disconnector cam surface disposed for engagement by saiddisconnector engaging projection of said hammer hook, said disconnectorcam surface being of substantially straight configuration; adisconnector spring having force transmitting engagement with saiddisconnector and said trigger body and urging said disconnectorpivotally toward said trigger hook; a disconnector hook cam surfacebeing defined by said disconnector hook and being engaged by saiddisconnector engaging projection of said hammer hook during returnrotation movement of said hammer an angulated timing surface extendingfrom said disconnector cam surface and having intersection with saiddisconnector hook cam surface, said angulated timing surfaceestablishing a greater length of said disconnector cam surface achievingdelay of hammer reset and preventing doubling of firing activity duringuse.
 10. The multi-stage trigger mechanism of claim 9, comprising: 2.The multi-stage trigger mechanism of claim 1, comprising: saiddisconnector spring being a coil type compression spring havinggenerally circular first and second ends; said spring retainer being aspring retainer projection having an undercut portion defining a springopening and retaining said first end of said coil type compressionspring.
 11. The multi-stage trigger mechanism of claim 9, comprising: adisconnector stop member being defined by said trigger body and having astop surface limiting spring urged pivotal movement of said disconnectorrelative to said trigger body.
 12. The multi-stage trigger mechanism ofclaim 9, comprising: a trigger rotation limit projection being definedby said trigger body and being disposed for contact with a firearmreceiver and preventing over-rotation of said trigger body.
 13. Themulti-stage trigger mechanism of claim 9, comprising: a hammer engagingcam surface being defined by said disconnector; and a disconnector searbeing defined by said disconnector and having a hammer engagement camsurface and a disconnector sear projection establishing a hammer returncam surface of sufficient length to hold said hammer down sufficientlyto prevent following, a portion of said hammer engagement cam surfacebeing a second stage cam surface.
 14. The multi-stage trigger mechanismof claim 13, comprising: said hammer engaging cam surface being ofsubstantially planar configuration; and said disconnector searprojection establishing a surface disposed in angular relation with saidhammer engaging cam surface.
 15. The multi-stage trigger mechanism ofclaim 9, comprising: a pair of spaced disconnector mount flanges beingdefined by said trigger body and having apertures formed therein; and apivot pin extending through said apertures of said spaced disconnectormount flanges and through said disconnector member and mounting saiddisconnector for pivotal movement about said pivot pin.
 16. Themulti-stage trigger mechanism of claim 9, comprising: said disconnectorhaving a hammer contact surface and a timing surface having intersectionwith said first surface and being disposed in angular relation with saidhammer contact surface, said angular timing surface causing said hammercontact surface of said disconnector to be of sufficient length to holdsaid hammer down during return for a sufficient period of time toprevent doubling during firing activity.